The present invention relates to a novel antiserum. More particularly, the invention relates to an antiserum for immunohematologic agglutination reactions involving IgG antibodies.
In blood typing and crossmatching procedures, erythrocytes are contacted with serums to determine the antigenic characteristics of the erythrocytes, the antibody composition of the serum, or the compatibility of patient and donor blood. Frequently, reagent erythrocytes or antiserums, whose antigenic or antibody content are known, are used to characterize patient serum or cells. In typing procedures, the antigenic composition of patient red cells is determined by contacting those cells with various antiserums, and reactivity is measured by observing whether or not the cells agglutinate. Agglutination is a positive reaction indicating the presence of antigens corresponding to antibodies contained in the antiserum employed in the reaction.
The antibodies employed in the major blood grouping procedures, e.g., for types A, B, O, and AB, are IgM antibodies. Such antibodies are thought to be polyvalent, and can cause direct cell agglutination in saline solution. Thus, these antibodies are variously referred to as complete antibodies, direct agglutinins and saline agglutinins. There are important antibodies of the IgG class, notably those employed in Rh typing, which are thought to be divalent and which directly agglutinate cells only weakly in saline, or not at all. Means have been devised for potentiating reactions involving IgG antibodies so that they will directly agglutinate cells having their corresponding antigens. A widely accepted potentiating technique is to employ albumin in the suspending medium in a relatively high concentration. Diamond, L. K., and Denton, R. L., J. Lab. Clin. Med., 30, 821 (1945). This procedure is useful, especially when results are needed promptly, but it suffers from several disadvantages, the most important of which is that it sometimes causes agglutination of sensitized red cells (i.e., false positive tests).
Early investigators reported that IgG antibodies could be converted to direct agglutinins by chemical reduction. For instance, Chan, P. C. Y. and Deutsch, H. F., J. Immunol., 85:37 (1960) reported that Rh antibodies of the IgG class could be converted to direct agglutinins by chemical reduction with 2-mercaptoethanol. This observation has been confirmed by subsequent investigators. For instance, Romans et al., Proc. Nat. Acad. Sci., 74:2531 (1977) reported results of experiments in which unpurified antibodies in whole serum were reduced with 2-mercaptoethanol, dithioerythritol, and dithiothreitol to yield direct agglutinins. The Romans, et al. work focused on the Rh and Kell antigens.
Heretofore, the interest in chemically reduced antibodies has been largely academic. The procedure has been employed to differentiate IgG from IgM antibodies (IgM antibodies are destroyed by chemical reduction), but until recently, it has not been commercially employed for the preparation of blood grouping serums. The primary reason that the procedure has not been accepted commercially is that direct agglutinins resulting from chemical reduction have very weak reactivity and require lengthy incubation times. The reactivity of such antibodies has been observed to be inferior to that of the same antibodies which had not been chemically reduced, but merely potentiated with albumin.